The invention relates to a method of detaching a film of material from a substrate.
Recently, semiconductor device packaging techniques have been developed in which a semiconductor chip is mounted on a substrate and an epoxy resin material is molded around the semiconductor chip on only one side of the substrate. Hence, the underside of the substrate is left substantially free of the epoxy resin material. One particular type of packaged device where this technique is used is commonly known as a quad, flat, no lead (QFN) package where the substrate is a metal lead frame. In order to prevent epoxy resin material seeping onto the underside of the lead frame and causing flashing, it is conventional practice to attach an adhesive masking tape to the underside of the lead frame. The lead frame with semiconductor chip and masking tape is then placed into a mold and epoxy resin material is molded around the semiconductor chip. The masking tape minimises seepage of epoxy resin molding material onto the underside of the lead frame, and so helps reduce flashing.
However, one of the problems with using masking tape to minimise flashing on the underside of the lead frame is the subsequent processing of the lead frame to detach the adhesive masking tape from the lead frame without damaging the lead frame or the packaged device.
In accordance with a first aspect of the present invention, there is provided a method of detaching a film of material from the surface of a substrate, the method comprising engaging a fluid delivery device with an aperture in the substrate from the opposite side of the substrate from which the film is attached to the substrate, and causing the fluid delivery device to pass a fluid through the aperture to generate a detaching force between the film of material and the surface of a substrate adjacent to the aperture.
Preferably, the method further comprises inserting the fluid delivery device through the aperture from the opposite side of the substrate to which the film is attached, and pressing the fluid delivery device against the film to separate the film from the surface of the substrate adjacent to the aperture prior to passing the fluid through the aperture.
In accordance with a second aspect of the present invention, there is provided a method of detaching a film of material from a surface of the substrate, the method comprising attaching a detachment member to the external surface of the film opposite to the surface of a substrate such that the attachment force between the detaching member and the film is greater than the adhesion force between the film and the surface of a substrate, and moving the detachment member away from the surface of the substrate to cause the film to detach from the substrate.
Preferably, the first aspect of the invention may be used in combination with the second aspect of the invention to remove the film from the substrate.
Typically, the first aspect of the invention is used to initiate detachment of the film from the substrate and the second aspect of the invention is used to remove the film from the substrate.
In one example of the invention, the detaching member may comprise a second film of material which is attached to the exposed side of the first film, typically by an adhesive. Typically, where the first aspect is used in combination with the second aspect, the second film is attached to the first film before the fluid is passed through the aperture in the substrate by the fluid delivery device.
Preferably, the second film comprises a layer of adhesive.
In a further example of the invention, the detaching member comprises a clamp device adapted to clamp onto an edge portion of the first film
Preferably, the aperture in the substrate is adjacent the edge portion of the first film which is engaged by the clamp device.
Preferably, the clamp member comprises a wedge shaped member which is adapted to be inserted between the first film and the substrate and a clamp member movable relative to the wedge shaped member to cause the film to be clamped between the wedge shaped member and the clamp member when the clamp member moves to a clamping position.